title: Self-association studies of the bifunctional N-acetylglucosamine-1-phosphate uridyltransferase from Escherichia coli.
abstract: The N-acetylglucosamine-1-phosphate uridyltransferase (GlmU) is a key bifunctional enzyme in the biosynthesis of UDP-GlcNAc, a precursor in the synthesis of cell wall peptidoglycan. Crystal structures of the enzyme from different bacterial strains showed that the polypeptide forms a trimer through a unique parallel left-handed beta helix domain. Here, we show that the GlmU enzyme from Escherichia coli forms a hexamer in solution. Sedimentation equilibrium analytical ultracentrifugation demonstrated that the enzyme is in a trimer/hexamer equilibrium. Small-angle X-ray scattering studies were performed to determine the structure of the hexameric assembly and showed that two trimers assemble through their N-terminal domains. The interaction is mediated by a loop that undergoes a large conformational change in the uridyl transferase reaction, a feature that may affect the enzymatic activity of GlmU.
authors.affiliation: Department of Biochemistry, Groupe de recherche axé sur la structure des protéines, McGill University, Montreal, QC, Canada H3G 0B1. jean.trempe@mail.mcgill.ca
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Trempe
authors.forename: Solomon
authors.initials: S
authors.lastname: Shenker
authors.forename: Guennadi
authors.initials: G
authors.lastname: Kozlov
authors.forename: Kalle
authors.initials: K
authors.lastname: Gehring
mesh_terms: D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry*; D008958:Models, Molecular; D009713:Nucleotidyltransferases / Q000737:chemistry*; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D053838:Scattering, Small Angle
chemical_list: D029968:Escherichia coli Proteins; D009713:Nucleotidyltransferases; C023226:UDPacetylglucosamine pyrophosphorylase